HP-97 display replacement

[teenix]

The 97 service manual has the pin out description of the display on the circuit diagram for the keyboard PCB.

You could use a 5VDC supply, connect each column in turn (marked as C1 - C14) to -ve via a flying lead, then using another flying lead connect the +ve via a 1K resistor one at a time to the LED anodes, (marked as SA- SG)

Note that digits 1 and 13 on the 15 digit display only have a negative segment because they only ever light up as positive or negative (mantissa / exponent), all the other segments are physically missing. To make things simpler HP engineers only used 1 column to drive these negative signs hence there is no column 15. (same as on the HP-67)

Column 12 is the common for the 2 negative signs.
Mantissa sign is segment SE
Exponent sign is segment SG

I don't know if it applies to all Topcats, but removing the LED display module from its connector can be difficult because the single conductor wires are a tight fit. Too much wiggling trying to remove the ribbon cable can break the wires.

cheers

Tony